A Community Antenna Television ("CATV") system, or cable television system, includes at its basic elements a centralized transmitter and a distribution network. The centralized transmitter typically includes an aerial antenna for receiving radio frequency ("RF") television signals. The centralized transmitter is further connected to communicate television signals to CATV subscribers through the distribution network. The distribution network includes an array of coaxial cable, repeater amplifiers, and other devices that often connect as many as hundreds of thousands of subscribers to the centralized transmitter. The complexity and size of the distribution network require that network operation and performance be periodically tested and/or monitored.
One test often performed by CATV service providers is leakage detection. Leakage detection is an operation which measures the leakage of CATV signals to the exterior of the distribution network. CATV signal leakage occurs in faults or anomalies within the distribution network. For example, if a portion of the coaxial cable is insufficiently shielded, then significant levels of CATV signals may leak to the environment surrounding the cable. Government regulations limit the amount of permissible CATV signal leakage. Accordingly, service providers employ leakage detection to determine compliance with government regulations and otherwise obtain information as to the performance of the distribution network.
A common method of leakage detection consists of physically scanning the distribution network with a portable leakage detector. Specifically, a technician drives or walks along the route of the distribution network with an activated portable leakage detector. The leakage detector, which includes an RF receiver, measures the level of RF signals within the CATV spectrum and provides an indication of that level to the technician. Accordingly, if a technician passes by a portion of the distribution network in which a leak is present, a relatively high signal level will be measured.
A number of leakage detection devices are presently known. In connection with industry and regulatory standards, such devices typically are tuned to detect and/or measure leakage signals in the frequency range that overlaps with frequencies allocated for aeronautical use. Specifically, a typical leakage detector is tuned to receive a select television signal having a CATV channel frequency of between 115 MHz and 140 MHz. In order to distinguish leaked CATV signals from other sources of RF energy, the leakage detection device measures energy in an extremely narrow band around the CATV channel frequency. Such a measurement has a higher probability of being representative of actual CATV leakage signals, as opposed to RF signals from other sources.
To achieve a signal strength measurement in such a narrow signal band, the leakage detectors typically down-convert the received RF signal to an intermediate frequency substantially below the 115 MHz range. Such frequency conversion allows for the use of conventional filters to produce the required narrow bandwidth signal. The Searcher Plus leakage detector, available from Trilithic, Inc., operates in this manner.
The one problem associated with presently available leakage detection devices, and in particular, those that use the frequency conversion step referenced above, is power consumption. The various electronic circuitry within the leakage detectors, including the frequency conversion circuitry, consumes a significant amount of power. High power consumption is problematic in part because leakage detectors are typically battery-powered. Specifically, it has been observed that batteries within portable leakage detectors frequently require recharging or replacement. Frequent battery recharging and/or replacement can be inconvenient from the perspective of the field technician.
While advances in battery technology may improve battery charge-life to partially overcome the need to frequently recharge or replace the batteries in leakage detectors, there is nevertheless a need for leakage detection equipment that consumes less power while providing the sensitivity and capabilities that are currently available.